Field
Aspects of the present invention relate to a wavelength converter and a liquid crystal display (LCD) including the same.
Discussion of the Background
Liquid crystal displays (LCDs) are of great importance in information display technology. An LCD includes liquid crystals inserted between two glass substrates. The LCD displays information by using electrodes disposed on the glass substrates to control the orientation of the liquid crystals. Here, a color filter included in the LCD passes light of a particular wavelength band only, and realizes various colors by combining the light, so that the various colors can be seen by a viewer.
The color filter generally includes red, green and blue filters, and passes light of a wavelength band having a color of a corresponding region only. Currently, research is being conducted to increase the color purity of light emerging from the color filter, by using quantum dots.
A quantum dot, which is a nano-sized semiconductor material, exhibits a quantum confinement effect. The quantum dots emit stronger light than typical phosphors in a narrow wavelength band. The emission of the quantum dots occurs when excited electrons move from a conduction band to a valence band. Although the quantum dots are formed of the same material, the wavelength of emitted light may vary with the size of the quantum dot. As the size of the quantum dot is smaller, light having a shorter wavelength is emitted. Thus, light having a desired wavelength region can be obtained by adjusting the size of the quantum dot.
The quantum dot emits light even at a corresponding excitation wavelength. Thus, when several kinds of quantum dots exist, various colored light can be observed at a time, even though each quantum dot emits at a single wavelength. Furthermore, since the quantum dot only moves from a ground vibration state of the conduction band to a ground vibration state of the valence band, the emission wavelength is almost monochromatic light. When the quantum dot is used, a desired color can be obtained by adjusting the concentration or size of the quantum dots, as compared with when phosphors are used.
However, even when quantum dots are used, since light of wavelength regions of two or more colors is emitted, color mixing may occur in an area where wavelength bands of different colors are adjacent to each other. Accordingly, a wavelength band in which color purity is reduced may exist, making it difficult to realize a high-purity color.